Heat sink



FIG. 1 shows a perspective view of a heat sink according to the present invention.

FIG. 2 shows a top view of the heat sink of FIG. 1, the bottom view being a mirror image of the top view.

FIG. 3 shows a front view of the heat sink of FIG. 1, the rear view being a mirror image of the front view; and,

FIG. 4 shows a right side view of the heat sink of FIG. 1, the left side view being a mirror image of the right side view.

Portions or features of the heat sink shown in broken lines form no part of the claimed design. 

The ornamental design for a heat sink, as shown and described. 